In radio access networks (RAN), traffic can be conveyed using the Common Public Radio Interface (CPRI) format, from e.g., a Base band unit (BBU) (containing a Radio Equipment Control (REC)) to a remote radio head (RRH) where the Radio Equipment (RE) is located.
When the Radio Equipment Control and the Radio Equipment are located at a distance from each other, CPRI supports that data on layer 1 (physical layer) can be transmitted from the REC to the RE using an optical interface. In other words, an electrical signal can be modulated onto an optical channel and transmitted as an optical signal over the optical interface, e.g. fiber, to the receiving side where it is demodulated into an electrical signal again, which is conveyable to a client interface. When the RE is located remote from the REC, the REC and the RE can be interconnected via an optical transmission line.
There is a constant desire to improve the performance and robustness in networks. This is also the case for radio access networks.